| Electro-hydraulic proportional directional valve can not only achieve a balanced switch direction without changing the pressure, but also finish the remote throttling governing. On behalf of the development of the hydraulic direction control, it is widely used in engineering machinery, mechanical processing industry, rubber machinery, metallurgical industry, the entertainment industry, shipbuilding and textiles. Its technology level reflects a country’s level of industrial development to some extent, thus all countries in the world attach great importance to the research of electro-hydraulic proportional directional valve.Due to the limited thrust of proportional electromagnet, conventional direct-acting electro-hydraulic proportional direction valve has limitations of small flow and pressure. Thus, the pilot electro-hydraulic proportional direction valve has to be applied in some situation of the large flow, however, the pilot valve has limitations of complex structure and can not work at a zero system pressure. In order to change this situation, upon the background of National Foundation of Natural Sciences,"Fundamental research for key technology of2D electro-hydraulic proportional directional valve integrated with direct-driven and pilot control approaches " and a major project of Zhejiang Provincal Natural Science Foundation of China,"Fundamental research for key technology of2D electro-hydraulic proportional reversal (throttling) valve", a new electro-hydraulic proportional directional valve, which was composed of2D directional valve (flow valve), compression torsion coupling and proportional electromagnet in a line, was proposed to enhance the working flow and pressure by a large margin. At the same time, the struction of the valve was simplified and it could also be realized at the zero system pressure as direct-acting electro-hydraulic proportional direction valve did. Therefore, this reasearch has not only the important engineering application value, but also the great theoretical value for the electro-hydraulic proportional direction valve technology.The main research works and achievements of this paper are as follows:(1) Since the direct-acting electro-hydraulic proportional directional valve can not work normally in the high pressure and large flow, and the structure of pilot electro-hydraulic proportional direction valve is complex, so the function of conductivity-controlled electro-hydraulic proportional valve is achieved by double degrees of freedom of spool (rotating and sliding). Output pressure of the hydraulic resistance the bridge changes by rotating spool, then the static pressure drives the spool produce axial movement. The characteristics, structure and working principle of the2D electro-hydraulic proportional directional valve are analyzed, and the mathematical model of pilot stage is established.(2) The thrust of proportional electromagnet is far less than the fluid power (also called Bernoulli force), but the tangential resistance of spool is small, so the compression torsion driving technology is proposed. The compression torsion coupling is used to realize motion conversion and amplify the thrust force of proportional electromagnet, therefore the unfavorable influence of friction force between spool and valve sleeve on proportional characteristics can be effectively overcome.(3) The structure and working principle of casing bi-directional proportional electromagnet are analyzed, and the mathematical model is established. On this basis, the casing bi-directional proportional electromagnet is designed by using the electromagnetic simulation software of Maxwell. The simulation results show that the size and strength of the casing bi-directional proportional electromagnet is smaller than magnetic isolation rings stye proportional electromagnet. In the working stroke section, the horizontal characteristic is good. The segmented sinusoidal curve is used to simulate the saturation and hysteresis in electromagnetic circuit of the proportional electromagnet, and the theoretical and experimental results have good consistency.(4) According to the mathematical model of the2D electro-hydraulic proportional directional valve, stability of pilot stage are analyzed by Linear system theory analysis. It is analyzed that the key design parameters of Flexible compression torsion coupling-type2D electro-hydraulic proportional valve affects the dynamic characteristics of pilot stage by using the MATLAB software. The simulation results show pilot stage has good dynamic characteristics in a stable condition; To verify the static and dynamic characteristics of the valve, a test platform of the valve is built. Experiments showed that:the leakage of pilot stage is0.2L/min; the flow rate is190L/min at27MPa; the hysteresis is less than4.5%; the bandwidth is4Hz corresponding-90°; and the rise time of step response is about0.55s.(5) The dynamic characteristics of the ball screw-type2D electro-hydraulic proportional valve is simulated by using SIMULINK, and results of the simulation provide a theoretical basis for the design of the valve. To verify the static and dynamic characteristics of the valve, a test platform of the valve is built. Experiments show that the maximum flow rate is approximately95L/min and the hysteresis is less than6.5%with pressure7MPa; the hysteresis is less than8.5%and the maximum flow rate is approximately140L/min with pressure15MPa. The bandwidth is3.5Hz corresponding-90°; and the rise time of step response is about0.6s. Finally, it is analyzed that the difference of structure and properties between a ball screw-type2D electro-hydraulic proportional valve and2D digital valve. |
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